JPH03504372A - crystalline molecular sieve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] crystalline molecular sieve The present invention relates to crystalline molecular sieve compositions, in particular frameworks. + trivalent elements, such as aluminum, skeletal S* elements, such as phosphorus, and preferably A crystalline molecular sieve set containing a skeleton and a 44-valent element, such as silicon. Regarding products.

Zeolite materials, both natural and synthetic, are suitable for various types of hydrocarbon conversion reactions. It has been known for a long time to have a catalytic action. Some zeolite materials are , a large number of small cavities, such as those connected by a large number of very small channels or holes. Have a tee, X! An ordered, porous structure with a well-defined crystalline structure identified by single diffraction. It is an aluminosilicate. These cavities and pores are unique to each particular zeolite material. have a uniform size. The dimensions of these pores are such that adsorbed molecules of a certain size cannot be accepted. molecules with larger dimensions are excluded. These properties became known as "molecular sieves" and It has come to be used in many fields.

These molecular sieves contain a wide range of cation-containing bonds, both natural and synthetic. There are crystalline aluminosilicates. These aluminosilicates contain Sin, and Al. It has a rigid three-dimensional skeleton of 04, and this tetrahedron is acid j! Aluminum sharing atoms The ratio of the sum of umium and silicon atoms to the oxygen atom is 1 = Special Table 103-504372 C2) It can be expressed as 2. Electron valence of tetrahedron containing aluminum , when cations such as alkali metals and alkaline earth metals are incorporated into the crystal, K. It is balanced. This is due to aluminum 7 various cations such as C/2, S It can be expressed as the ratio of the numbers of D/2, N8, K or L(, is equal to IK. One data One type of cation can be completely transferred to another type using well-known ion exchange techniques. can be partially replaced. By such cation exchange means, the given alkali The properties of the minosilicate can be varied depending on the choice of cation.

Many types of synthetic zeolites are made by known techniques. These zeolas For example, zeolite A (USF 2,882,243), zeolite (USF 2.882.244), Zeolite l' (USF 3,130゜0 07), Zeolite ZlK-5 (USP 3,247,195), Zeolite ZK-4 (USF 3,314.752), Zeolite ZSM-5 (USF 3 ,702,886), Zeolite ZSM-11CUSF 3.709.979 ), Zeolite ZSM-12 (USF 3,832.449), Zeolite Z SM-20 (USF 3,972.983), Zeolite ZSM-35 (USF 4,016,245), Zeolite ZSM-38 (USF 4,046,85) 9), and zeolite ZSM-23 (USF 4,076.842) It is indicated by a display or symbol that indicates that

Aluminum phosphate is described, for example, in USP 4,310.440 and 4,385, 994.

Silicoaluminophosphates of various structures are disclosed in USF 4.440,871. It is. USP 4,363,748 is a low acid activity catalyst for oxidative dehydrogenation. discloses a combination of calcium and aluminum monocalcicum-cerium phosphatate. Ru. BP 2,068,253 uses silica and aluminum as a low acid activity catalyst for oxidative dehydrogenation. A luminium-calcium-tungsten phosphate combination is disclosed.

USP 4,228.036 is a zeolite for use as a cracking catalyst. Alumina-aluminum phosphate-silica as the amorphous body to be mixed with Rix is disclosed. USP 3,213,035 is aluminosilicate catalytic It is disclosed that the hardness of the medium is controlled by phosphoric acid treatment. This catalyst is amorphous .

The present invention provides crystalline material bundles with X6 diffraction edges as shown in Table 14 below from at least 70 weight A novel synthetic crystalline molecular sieve composition.

16.4±0.2 City-8,2±0.1 Zeng 6.19±0.07 Change 5.48±o, os 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　More specifically, the following 5 with diffractive edges.

Table IE 16.4±0.2 *a8.2±0.1 6.19 ± 0.07 Revenge 5.4 8±0,05 so 4.74±(105w 4, lO±0.04 m4.05±O,04m 3.76±0.03 m3.28±0.03 Suga these x! 1 Diffraction data was obtained using copper X-alpha irradiation, This is what I got from the @ system. The position of the peak represented by 2 degrees theta (ri) is 2 degrees theta. (Here, theta is the Bragg angle.) Lattice spacing d (o ) and the relative strength of the line, I/'*, C1m is the strongest The system of line intensities (subtracting the background) was calculated. The relative strength is the symbol ea = very strong (75-100%), 1 = strong (5G-74%), gift = medium (25- 49%), Suga=weak (0-24%). This X! 1st diffraction pattern is book This is common to the main components of the composition of the invention. Ionic exchange of cation y with another cation Although the lattice spacing may shift slightly and the relative intensity may change when , resulting in compositions that exhibit substantially the same X-ray diffraction pattern. Also the relative strength of the individual lines , for example, it can change in correlation to the strongest 11 due to chemical treatment such as ssi: treatment. sample set Other variations may occur depending on the composition and degree of heat treatment5. The relative strength of the lines depends on the channel structure. It can also vary depending on factors such as adsorption of water, hydrocarbons, and other components during production. Ma The optical system of the X6 diffractometer also has a large effect on the intensity, especially the intensity in the low angle range. I'll accept it. Strength can also be affected by preferred crystal orientation. Also 6, 19±0. The d-spacing line of 07A has a double amount at 6.21±0.05j and 6.17±0.05A. K, but in many cases it is difficult to resolve this double line. .

The X6 diffraction lines in Tables IA and IB show the crystal skeletal topology showing large pores with 18-membered Rt - represents. The pore has a diameter of at least 12 angstroms, e.g. It is 12-13 angstroms.

The crystalline skeleton of the composition of the present invention has the chemical formula of [2CX0t)v-y:C Y’t); 1-11: (”t)s+y where X is +311m yuan 9, Y has a +5 valence element, 2 is a +4i11+ element, and 1 and 1 are each like -1. The value is larger than +1, and the anion and/or cation is electrically neutral. Must keep! may exist depending on the Preferably, element Z is present, and S and 1 have the following relationship: Satisfied: (1) When 1 is 00, 1 is not 0. @ When 1 is 00, the cloud is not 0, (3) g+y is greater than 0.001 and less than l @+31 in the above composition i element X is preferably aluminum, chromium, vanadium, molybdenum, arsenic, Selected from antimony, manganese, gallium and boron, +441 element 2 is preferred or selected from silicon, germanium and titanium, and the +5 valent element Y is preferably selected from silicon, germanium and titanium. selected from phosphorus, arsenic, antimony and vanadium. Most preferably X is al Y is phosphorus and %Z is silicon.

The values of 1 and 1 indicate that the composition has a cation exchanger with potential for use as an acidic catalyst. It can be an anion exchange material with potential for use as an anion exchange material or as a basic catalyst.

The composition of the present invention contains a source of X oxide, Yal oxide and Z@ oxide, water, and an organic directing agent. 1 by making a reaction mixture containing an inorganic cation M and an anion N iea will be done. This reaction mixture has the following relationship: (J')s: (M, O ) h : (Xi’s) # : (ZOt)t : CY*Os), : (A ’), : 嘱’)hHere, 6%-1-1d, a, f%I, and 5 satisfy the following relationship. is the number: dlCd+2m+2m) is 0.2 or less (preferably 0.05-a/(d+ 21 + 21) is 0.2-0.4, preferably a number that further satisfies the following relationship: is: ni/(a+d+e) is less than 2 t/(a+d+a) is less than 2, h/(a+d+m) is 3-150° The initial νB of the reaction mixture is preferably 4-6. This mixture was stirred for 130-150 min. ℃ and maintained at this temperature until oxide crystals are formed.

, E are controlled during the reaction such that the final νH is 6-7, thus at least 70%, Preferably produces at least 80% of the composition of the invention (based on the weight of total crystalline phase) The reaction is usually complete after 4-20 hours. Separation and recovery of crystalline product from reaction medium do. This can be done, for example, by cooling the whole thing to room temperature, filtering it, washing it with water and drying it. [to be carried out]

In some cases it may be preferable to use a two-phase reaction mixture. In this case, X, Y, Z @ small amount of compounds Dissolve or disperse at least 1 in an organic solvent.

The above reaction mixture composition is prepared from the appropriate materials to supply each component. I can do it. Useful sources of +trivalent elements such as Al<=Rum include known forms of oxides or Examples include hydroxides, organic or inorganic salts or compounds. Usefulness of +4 pleasant elements such as silicon Sources include known forms of dimetrite or silicic acid, alkoxy or other forms of these elements. There are compounds such as

Useful sources of +55 valent elements such as phosphorus include phosphoric acid or phosphorus oxides in known forms, phosphorus ate and phosphite, and organic enzyme conductors of these elements.

The organic solvent may be any other suitable organic solvent which is substantially immiscible with water in alcohol. There are liquid compounds.

Organic directing agents include organic mono- or dialkyl amines (alkyl is carbon a3 or carbon 4) and There are onium compounds of the following formula: E4M"X- or (RsM"R'M+B,)X.

where R or R' is alkyl of carbon@1-20 or a combination thereof, and M is 4-carbon alkyl; (e.g. nitrogen, phosphorus, arsenic, antimony or bismuth), where X is a ions (e.g. fluoride, chloride, promide, iodide, hydroxy acetate, nal7ate, carboxylate). particularly preferred orientation As agents, tetraethylammonium hydroxide, tetrapropylammonium mupromide, more preferably tetraethylammonium hydroxide and dia Rukylamine (butyl is preferred as alkyl, and propyl is more preferred) There is.

In order to suppress the formation of unintended crystal phases, the temperature was kept within the above range of 13G-155℃. There are certain views that must be carefully controlled.

The preferred temperature of this la concave circle depends on the directing agent used [dipropyl amine When using a thermoplastic resin, the temperature is preferably 135-155°C, particularly preferably 150°C or higher. On the other hand, in the case of tetrapropylammonium hydroxide, the temperature is preferably 130-145°C. Preferably, the temperature is 135°C or higher.

In its synthesized form, the composition of the present invention contains microporous voids that are trapped during the synthesis process. It may contain organic directing agents and water molecules trapped therein. However, these are due to @ Can be removed.

The cations from which the compositions of the invention are synthesized can be prepared by means well known in the art. , at least a portion thereof may be substituted by other cations. Preferred substitutions Thiones include metal ions, hydrogen ions, and hydrogen precursors such as ammonium and ions. and mixtures thereof. Particularly preferred cations treat the composition catalytically active. or control catalyst activity (particularly for hydrocarbon conversion reactions). child These include hydrogen, rare earth metals, and the periodic table of elements IA, flA, ■A, ■A, IB. , ■B, ■B, ■B, ■B, and ■ group metals.

A typical ion exchange method involves contacting the synthesized composition of the invention with a salt of the desired replacement cation. This is a way to make them touch each other. These salts include halides such as chloride, nitrates, and sulfates. There is.

The crystalline composition of the present invention can be prepared at K. before or after ion exchange.

Heat treatment is preferred. This heat treatment uses air and nitrogen.

Under an atmosphere of hydrogen, steam, etc., 300-1100°C, preferably 350-750°C ℃ for 1 minute to 20 hours. This heat treatment can be carried out either under reduced pressure or under pressure. However, atmospheric pressure is preferable in terms of ease of handling.

Other materials that can withstand the temperatures and other conditions used in various organic transformation reactions may be added to the compositions of the present invention. It is preferable to add a quality or matrix. These substances also have active properties. Synthetic zeolites, natural zeolites, clays, silica and/or metal acids There are inorganic substances such as compounds such as alumina. Catalyst set containing the composition of the present invention The products are usually original F! All1Ji5! material 1-90% by weight and matrix material 1 It consists of 0 to 90% by weight. A more preferred catalyst composition is 2 to 80% by weight of the composition of the present invention. % and matrix 20-98% by weight.

By using active substances in combination with the compositions of the invention, certain organic modifications are possible. The conversion and/or selectivity across the catalyst of the conversion process can be varied. inactive Substances act as diluents to control the amount of conversion in a given process, limiting the rate of reaction. It is possible to process the product economically and on schedule without using other means of control. make it possible.

These substances are used to improve the crushing strength of the catalyst under industrial operating conditions. It is added to natural clays such as bentonite and kaolin. This substance, namely clay , oxides, etc., act as binders for the catalyst. In industrial use, the catalyst is crushed. ``It is desirable to avoid forming C1# powder, so a catalyst with high crushing strength is used. It is desirable to provide. These clay binders are usually exclusively catalytic. It is used to improve the crushing strength of bodies.

Natural clays that can be combined with the novel crystals of the present invention include montmorillonite and kaolin. (including subbentonite), and Dixie-clay, McNamee-clay, and Jojo clay. - Kaolins or main mineral components known as shea clay and fluorid clay, etc. is halloysite, kaolinite, diffukite, natalite or anuxite There are other things that are. These clays can be used in their as-mined state or in their calcined, acid-treated or Can be used in a chemically modified state.

In addition to the above substances, the composition of the present invention also contains aluminum phosphate, silica-alumina, Silica-magnesia, silica-zirconia, silica-thoria, silica-beryria , porous matrix materials such as silica-titania and silica-alumina-thoria, Silica-alumina-zirconia, silica-alumina-magnesia and silica-ma A ternary composition such as Gnessia-Sirconi 7 can be composited. The microcrystalline material of the present invention and The relative proportions of the inorganic oxide gel matrix can vary over a wide range. Crystals of the invention The content of beads is 1-90% by weight of the composite, more commonly this composite is When it is made into a shape, it is preferably 2 to 80% by weight.

When the composition of the present invention is used as a catalyst component in a catalytically active form, a water bulking component may be added. It contains 5, but the reforming beam using this 7 ohming raw material is heated to a temperature of 37o -540℃, pressure 100-1000pajy (791-6996KIls), Preferably 200-7001aig (1480-492 gjPs), liquid time Space velocity 0.1-10, preferably 0.5-4, hydrogen/hydrocarbon molar ratio 1-20 , preferably using conditions of 4 to 12.

The catalyst consisting of the composition of the present invention can be used in combination with a water bulking component such as platinum to produce normal paraffin. It is used for the hydrogenoisomerization of Hydroisomerization is carried out at a temperature of 90-375°C, preferably 145°C. -290°C, liquid hourly space velocity 0.01-2, preferably 0.25-0.50, It is carried out at a hydrogen/hydrocarbon ratio of 1:1-5:1. This catalyst also It is also used for the isomerization of olefins or aromatics using temperatures of 200 to 480℃. Catalysts may also be used to lower the pour point of gas oils. This reaction has a liquid hourly space velocity of 10- 30, carried out at a temperature of 425-595°C. The composition of the present invention containing a metal such as platinum Other reactions that can use catalysts consisting of these compounds include hydrogenation-dehydrogenation reactions and desulfurization reactions. reaction, the polymerization of olefins (olipmerization), and the polymerization of alcohols (e.g. conversion of ethanol) or ethers (e.g. dimethyl ether) to hydrocarbons, Alkylation of aromatics (e.g. benzene) in the presence of alkylating agents (e.g. ethylene) There are other organic compound conversion reactions such as

The present invention will be explained in more detail below with reference to Examples and drawings.

FIG. 1 shows the X@ diffraction pattern of the product of Example 1 as synthesized.

FIG. 2 shows the X11 diffraction pattern of the calcined product of Example 1.

Figure 3 shows the X11 diffraction pattern of the calcined product of Example 3 at 10t Si (0C tHJa and 601F) an organic phase consisting of 1-hexanol and 2390H, PQ, (85%), 14r Al*Os, IOP J-P Ω pyramine (DPA) and 6010H,O to form a two-phase synthesis reaction mixture.

The reaction mixture had approximately the following overall composition:

S 4 /, 5 t + AI + P = 0.1DPA/S + AI + P = 0.2 The reaction mixture had an initial pH of 5.5 and was stirred for 15 minutes without heating, then heated to 50°C. /hour to 150°C and maintain this temperature for 24 hours, during which time the silicophosphor The mixture was stirred at 800 dj1m until aluminate crystals were formed. Finished forging B is 7 was.

This crystalline product was separated from the reaction mixture by filtration and washed with toluene and ether. Cleaned and dried. Next, a sample of the product was analyzed by X@, and the diffraction lines shown in Table 2AK were also obtained. It was confirmed that the composition was a molecular sieve composition. This sample's X! 1st diffraction The pattern is shown in FIG. The product was calcined at 450°C for 4 hours each in nitrogen and air. The X-ray diffraction pattern of the product is shown in Table 2B and FIG.

Table 2A ” 16.313 5.42 10010.847 8.15 29.315 9.4 9 3” 8.181 10.81 106.683 13-24 1””6.162 14.37 45.637 15.71 2” 5.455 16.24 1” 4.933 17.98 14J42 18.32 2” 4.731 18 ．． 75 34.341 20.45 24.206 2111 5” 4.087 21.74 8” 4.057 21. 90 74.005 22.19 3 − 3.963 22.43 7” 3.94 2 2155 73.828 23.23 3″3゜763 23.63 4” 3.636 24.47 13.580 24.86 1’ 3.419 26.06 1” 3.396 26.24 13.370 26.44 1:L349 26.61 1” 3.276 27.21 63.157 2g, 26 2L14 2 28.40 13.0g2 28.96 33.029 29.48 141 [Crystals with pore windows formed by 1 g of tetrahedral members exhibit skeletal topology] Diffraction- Diffraction lines with additional intensity contribution from other crystalline phases boneee double line Table 2B 4.377 20.28 14.349 20.4 2 14.311 20.8G 14 ．． 239 20.95 2” 3.934 2L 59 7:166g 24.26 1: LaB5 24.50 2L581 24.86 23L421 26.04 13.4 G5 26.16 1L365 26.48 13.32g 26.78 1L3 13 26.90 1 axis 3.277 27. 20 9L161 28.22 2L 129 28L52 13.0?9 28. 99 43.054 29.24 1 LO2396,542 A crystal with a pore window formed by -18 tetrahedral members exhibits a skeletal topology. broken line Diffraction lines of 0.0 plus additional intensity contribution from other crystalline phases Threat/Bone Double Line Analysis of the X11 data of the as-synthesized and calcined products revealed that the crystalline phase 80 weight of the crystalline material of the present invention having X11 diffraction lines listed in filA and IB. % or more.

Example λ The method of Example 1 was repeated. However, the reaction mixture was heated to 130°C at a rate of 50°C/hour. maintained at a temperature of 24 hours, heated to 200°C, then maintained at this temperature for 24 hours. Ta.

In this case, there are compositions with Xl [diffraction lines listed in Table 1A and JK, but it is Less than 70% by weight of crystalline product.

Example 3゜ Mixture containing 38.31F 85% orthophosphoric acid CHsPO &> in 502 water was mixed with 22.97 t of hydrated aluminum (Kaiser Aj!Os). child 1081f of tetra-7”a-bylammonium hydroxide (TPAO H25%) was added. In an autoclave under autogenous pressure at 135℃ for 16 hours r4jJ crystallized. The solid product was filtered, washed and dried. Figure 3 shows the combined state x of substance! Figure 4 shows the calcined product special table 13-50. 4372 (5) The yg11 diffraction pattern of (Nt'Ps: calcined at 538°C for 2 hours) is shown.

Tables 3 and 4 show the x1m powder diffraction data of the synthesized and fired samples, respectively. show.

These X! Analysis of the I information indicates that this crystalline product is X! in Tables 1A and B. ! diffraction It was found that it contains more than % of the SOW amount of wire-like minerals.

! ! 3 16.28921 5.425 100.013.40 839 6.592 2.411.96539 7J8g 4.211.41644 ’1.744 1.99.34245 9 ．． 466 0.1g, 10277 10.919 10J6.85344 12.917 0.36.15000 14.402 0.8 5.96600 14.848 G, 25.390 g3 16.443 2.44.66975 19.004 4J4.49586 19.74 6 1.84.38386 20.256 G, 94.24135 2G, 944 2.24.14340 21445 9.44.0 6627 21.857 1G, 14.01B65 22.147 7.83.94624 2 2.530 10.2 & 70654 24-008 10.13.53122 25.219 1.23.43123 25.967 1.8 3.3g755 26.308 1.33.246 45 27-473 3LIL103g3 28.762 3.33.04500 29.3 30 0.7 Table 4 16.4 B 362 5.361 100.011.98 198 7.378 G, 59.48430 9.324 0.78-20744 10.779 　　　　12. ．． 06.17372 14.346 L45.46674 16.213 1.0472 g 95 18.764 4.54.28024 20.752 1.04.08109 21776 10.83.95860 2λ459 7.8 3.83964 23.164 1.2:L759g5 23.663 7.4L63846 24.4 64 1.9L57871 24B 79 2.33.40920 26.13B 1.43.27 366 27.240 7.93.15541 28.282 2.5108239 2g, 966 2.6:40291g 29.486 13 correction Copy and translation of written documents) Submission form (Article 184-8 of the Patent Law) June 21, 1990 Commissioner of the Patent Office Yoshi 1) Moon Takeshi Dan 1 Display of patent application PCT/US 88104482 2. Name of the invention crystalline molecular sieve 3 Patent applicant East 42nd Street 150 Name Mobil Oil corporation 4 agent The scope of the claims small, The composition according to claim 1, comprising:

4 x and y have the following relationship: (i) When x is 0, y is not 0, (iii) When y is O, X is O (2) x+y is greater than 0001 and less than 1. 3. The composition according to 3.

5. The method according to claim 3 or 4, wherein X is aluminum, Y is phosphorus, and Z is silicon. Composition.

6. Water, source of oxides of elements X, Y and 2, organic directing agent D, inorganic cation M and anion N, with the following molecular relationship: (D), : 040) b: (X, 03 ). : (202), : (Y, 05), : (Solver+t), : OJ), : (g, O), where a/(d+2c+2eJ is less than or equal to 02) d/(d+2 c+2 e) is 0. Prepare a reaction mixture that satisfies 2 to 0.4, and convert this mixture to 130 to 155 4. The method according to claim 3, further comprising a step of heating at a temperature of 0.degree. C. for 4 to 20 hours. Method of manufacturing the composition.

7. The further relationship that the mixture is: a/(d+2 c+2 e) is 0.05 to 0.2, b/(c+d+ e) is less than 2, and c>e.

g/(c+d+e) is less than 2 and h/(c+d10) is 3- 7. The method of claim 6, wherein: 150.

8. The directing agent is dipropylamine and the temperature is 135-155°C. The method described in claim 5 or 6.

9. The directing agent is a tetrapropylammonium compound, and the temperature is 130~ The method according to claim 5 or 6, wherein the temperature is 145°C.

10. The method according to claim 5 or 6, wherein the initial pH of the mixture is 4-6.

12. The mixture comprises an aqueous phase and an organic phase, and at least one of the oxides is in the organic phase. dispersed or dissolved, and the mixture is stirred during the heating process to mix both phases. A method of claim 5 or 6.

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Claims (1)

[Claims] 1. A crystalline substance having an X-ray diffraction line as shown in Table 1A is Synthetic crystalline molecular sieve composition containing %. 2. A composition according to claim 1, wherein said substance has an X-ray diffraction line as shown in Table 1β. 3. The crystal skeleton of the substance has the following composition: ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ However, X is a +3-valent element, Y is a +5-valent element, Z is a +4-valent element, and s and y are each greater than -1 and less than +1, The composition according to claim 1. 4. The relationship between s and y is as follows: (i) When s is 0, y is not 0. (ii) When y or 0, s is not 0. , (iii) s+y satisfies greater than 0.001 and less than 1. composition. 5. 5. The method according to claim 3 or 4, wherein X is aluminum, Y is phosphorus, and Z is silicon. Composition. 6. Water, source of oxides of elements X, Y and Z, organic directing agent D, inorganic cations M and and anion N, and the following molecular relationship: (D)a:(M2O)b:(X2O2)c::(ZO2)d:(Y2O5)e: (Selvent)f:(N)g:(H2O)h Here a/(d+2c+2e) is 0.2 or less d/(d+2c+2e) is 0.2- A reaction mixture satisfying 0.4 was prepared and this mixture was heated at 130-155℃. A composition according to claim 3, characterized in that it comprises the step of heating to a temperature of 4 to 20 hours. How things are manufactured. 7. The further relationship that the mixture is: a/(d+2c+2e) is 0.05-0.2 and b/(c+d+e) is less than 2 fence, c e, f/(c+d+e) is less than 2, 7. The method according to claim 6, wherein h/(a+d+e) is 3-150. 8. The directing agent is dipropylamine and the temperature is 135-155°C. The method according to item 5 or 6. 9. The directing agent is a tetrapropylammonium compound, and the temperature is 130-1 The method according to claim 5 or 6, wherein the temperature is 45°C. 10. 7. A method according to claim 5 or 6, wherein the initial pH of the mixture is 4-6. 11. 11. The method of claim 10, wherein the final pH of the mixture is 6-7. 12. the mixture comprises an aqueous phase and an organic phase, and at least one of the oxides is in the organic phase; dispersed or dissolved, and the mixture is stirred during the heating process to mix both phases. 7. The method according to claim 5 or 6.